The present invention pertains to a device for indicating the fully charged state of a battery, especially a lead-acid storage battery, by determining the temperature of a recombination catalyst.
It is known that both excessively strong and excessively weak charging current levels are harmful to the life of a lead-acid storage battery. Generally, the charging of starter batteries and the like is controlled in accordance with voltage. However, voltage is not always a clear indication of the fully charged state because voltage is also influenced by other factors, such as by aging of the battery.
However, a lead-acid storage battery is always certain to be fully charged when oxygen and hydrogen evolve from the positive and negative electrodes in a stoichiometric ratio. Since this event is immediately imminent when a rise in temperature occurs in a hydrogen- and oxygen-recombining catalytic device, such a temperature signal has been used to control the charging process.
DE-OS No. 26 38 899 teaches that a lead-acid storage battery will generally lack approximately 10% of the amount of current needed for full charging at the time when the evolution of gas begins. This current is supplied in the form of an aftercharging current, the duration and intensity of which are set in a preselectable ratio with respect to the parameters of the original charging current. The time of the switch-over from the main charging phase to the aftercharging phase is determined by detecting the temperature rise occuring in a recombination device, which serves as a regulating variable.
To this end, DE-OS No. 30 20 606, which pertains to a data collection device for an automobile, teaches that a temperature signal sent from a catalytic converter is capable of being fed into a control circuit along with a battery voltage signal to provide such regulation.